Can't find much related to rake of the spreaders.

I've noticed a few Mozzies of varying ages with masts with swept back spreaders pretty much in line with the rear edge of the mast and was wondering what benefits this has particularly when so much forward mast bend is induced with modern sails and downhaul tension. Is it better to have the spreaders raked back or better to have them set at 90 degrees to the mast ?

If anyone has has thoughts on the issue I'd appreciate them.

Regards,

Peter

The fore and aft position of the diamonds attachment at each end also has a big effect on what the diamonds do to the mast.

I think, in general, the lighter crews put the spreaders further back to allow more bend to flatten the sail. But the mast is rotated so that effect is not so straightforward.

As for how tight, or what is fast, Bob Wilson always says he keeps adjusting them until the boat feels right!

For what it is worth- here is my take on spreader rake after having to re-rig mine. I am assuming it generalizes beyond my boat.
The more spreader rake the more you can induce pre-bend which, in the end, depowers the rig. This can be adjusted with the diamond wire tension (if there is spreader rake, if they are 90 deg then you wouldn't be bending anything really). I was told to not use a significant amount of prebend because I sail with a heavy crew (less pre-bend= more power for heavy crew). I assume high-end sailors will adjust their diamond wire tension to suit the conditions. The problem I have with all of this is this- I have about 1.5 inches of spreader rake with diamond wire tension actually pretty loose at about 250-300lbs which induces about 1.5-2 inches of pre-bend (maybe the mast is shot, who knows). Now add a spin and everyone starts talking about diamond wire tension more (to limit the S-bend). If I torque my diamond wires more to try to prevent that s-bend then I will end up with a lot more pre-bend than is necessary. Add to this is the fact that tightening the downhaul induces more pre-bend (thus depowering more) but doesn't really limit the s-bend (I think).
Well, I hope this gives you some idea about spreader rake,etc. I think I have succeeded in confusing myself

From what I can gather from the feedback both on the forum and around the traps (Thanks Garry) the raked spreaders are used for lightweight crews to induce mast bend and flatten the sail, sloop rig to even out the loading from the jib and for the spinnaker rig again to counter mast bend loading. In that case I will stick with the 90 degree spreaders on my cat rigged Mozzie. Thanks for the feedback.

I,m resurecting this topic because I finally got my new spreaders from Goolwa Masts for my new mast section. <img src="http://www.catsailor.com/forums/images/graemlins/cool.gif" alt="" /> Now I'm wondering where should I position them ? I've measured a few Mozzies at the yacht club and they don't appear to have the speaders centred. Should they be set dead centre between the mountings ? <img src="http://www.catsailor.com/forums/images/graemlins/confused.gif" alt="" /> Would the ones I measured have been set up to allow for jib leach ?

Assuming I put the hounds at maximum height where is a good height for the upper diamond mounts to avoid the diamond wires touching the stays during mast rotation ?

Any advice would be appreciated ?

Regards,

Peter

Hi Peter,

placement of upper attachment of Diamond wires I have always just looked at where the stays will clear them when mast is rotated. Markings on old mast may give you a good guide, if Hound and Diamond wire fitting to mast use the same method.

As a matter of interest I have heard people say that getting them as close to the hound fitting as possible, is one of the reasons for using T ball terminals. As they are generaly lower profile than any other method I have seen.

I have always placed spreaders in the middle of the diamond wire attachment points, don't know why just seemed right. I haven't heard any reason for doing it any other way.

Along with my own masts I have helped Tim, Peter and Neil build masts. Having a swaging tool and large riveter I tend to attract these jobs. Pity you are not closer.

Regards Gary. <img src="http://www.catsailor.com/forums/images/graemlins/tongue.gif" alt="" />

Peter

I have just been through the process of moving my upper spreader mount as I had a lot of binding of the diamonds on my side stay wires. I measured a mast at my club and the spreader upper mount was 300mm below the hounds. This is from the eye of the hounds to the upper hole of the spreader wire retainer (Ronstan style). Now when I did mine to this dimension I still have a little binding downwind as my system compared to the one I measured is slightly different styles... a bummer as I thought I had cured the problem for good. I initially had binding so bad that upwind the spanner would not rotate past the rear of the centre case... not good. So anyway I would look at spacing the top of the spreader retainers around 350mm from the eye of the hounds. I will be replacing my mast next season and will re do at 350mm...

Hope this helps..

Gary,

Thanks for the feedback. What are T Ball terminals, are they specifically for diamond wires and where do you purchase them ?

Regards,

Peter

Tony,

Thanks for the info. What a bugger that you didn't fully solve the problem last time around. <img src="http://www.catsailor.com/forums/images/graemlins/frown.gif" alt="" />

I'll go and take some more dimensions from my existing mast and other dimensions I took from other Mozzies.

Regards,

Peter

Unfortunately you can't even assume that much!
The general rule is that if you are carrying a heavy crew then you should put the hounds high to give the top of the mast the most support. If you are light you would set the hounds lower to allow the mast top to flex more and depower the main more easily.
I am a light-to-middle-weight cat-rigged sailor (72kg) and my hounds are right in the middle of the allowed range. This setup was also used by Chris Boag sloop rigged, with a very light crew - they couldn't have been more than 115kg combined. I hope that helps!


As far as binding on the sidestays is concerned, the position of the diamond attachments fore-and-aft will also affect whether they catch.

Tee-balls are stainless fittings which are pressed on to the end of the wire. They just hang in a reinforced hole in the side of the mast, and are easily removable from the mast. You have to find a rigger/chandler with the hydraulic press to make them up, and the fittings are not cheap.

Peter

The system I measured was a T-Ball setup I believe... I didn't know the name until it was mentioned in this post but the diamond wires hook into a slot in the mast, I know that. The system is very low profile compared to what I used, which is the Ronstan RF43A mast tangs with drilled out top hole to fit a 1/4" bolt and locknut. Due to this extra height I still have a little binding... I never stopped to think it would bind even at this distance (300mm) from the hounds. At least next time I will test (somehow) before I drill and rivet things together. Oh well, upwind I now have more power... Downwind I just need to pull the spanner around a little.

Cheers and good luck.

Tony,

I did some calculations based on my measurements and found that my distance from the diamond wires to the hounds was 240 mm. Another one I calculated was 145 mm so I don't understand why yours at 300 mm foul with the stays. What are the width of your spreaders ? <img src="http://www.catsailor.com/forums/images/graemlins/confused.gif" alt="" /> My new spreader is 580 mm from centre to centre of the wire holes.

Regards,

Peter

Tim,

Thanks for the info. I'm 86 kg so I assume that I'd be at the top of the hounds margin. Is that a good assumption ?

As for Tee Ball and the re-inforcing fittings, are they a Ronstan product or should I just take the whole setup to a rigging supplier and avoid the hassle ?

Regards,

Peter

At 86kg it would be reasonable to put the hounds high (somwhere between the middle and the top of the range).

Ronstan and Riley make the fittings but they are not the only ones. Most chandlery shops will stock them and many have the machine to attach them to the wire.

I just looked in the Whitworths catalogue and they only seem to have balustrading fittings which they call "Roll Swage Terminals". These are way too cheap to risk using on a boat so I would avoid them.

The Ronstan ones may be overpriced but they are certainly very expensive. Last time I looked it was $60 for one terminal. In practice, for Mosquitos these fittings look neat but are not necessary at all.

The standard swaged ends with a thimble will do the job, and you can do them yourself for a fraction of the cost. The tang for the top-end diamond fitting will work ok as long as it's positioned right. If building a mast I would just leave the diamond tangs till last and then put the mast up with them sticky-taped on - then you can move them around until they work.

Just so everyone knows what we are talking about here's the fitting in question on my mast.



You can't see the hole that the TEE is hanging in because I've filled it with Sikaflex. This is a problem with T-ball fittings - you are left with a large hole in the mast which you have to seal like this.

The reasons T-balls get used are that they don't stretch like swaged ends so your wires that are built to millimetric accuracy will stay accurate. They also look neat (except for the Sikaflex).

You can see the scuff marks on my mast from the sidestays. They go right up to the diamond fitting, so it seems this one only just works. Interestingly though, the little bit of Sikaflex on the tip of the Tee-ball is still there so the sidestays seem to just miss the Tee-ball.

The bearing points of the hounds and the Tee-balls are 300mm apart.

Peter

How odd... I will do some measurements over the weekend and get back to you.

Cheers

Peter

As promised.. see attached pic.

Centre of hounds hole to eye of upper diamonds - 280mm.
Upper diamonds to spreaders - 2300mm.
Spreaders to lower diamonds - 2600mm.
Lower diamonds to top of beam - 150mm.
Spreaders are 580 centre to centre.

Cheers

Tony

Is your mast by any chance raked forward?

I just realised that would make the sidestays more likely to catch the diamond tangs.

There was a time when Mosquitos (particularly sloops) had their rigs raked forward. These days they are almost never set forward of vertical, and any boat with the centreboard cases at their maximum aft position would have the mast raked back. Some cat rigged Mozzies (like mine) have quite a lot of aft rake.

Try dropping the mast back and see if it still catches.

Tim

My mast is vertical.. no rake for or aft... tell a lie it is 1/2 degree forward as there is a 1/2 degree bend in the mast at the spreaders.. so the top of the mast is directly above the base with the spreaders being 20mm forward of this point, effectively being in a neutral position. When I bought the boat it was raked aft but I could not get the helm balanced until I took out the rake. So if I am reading you correctly... you are saying that due to the position of my centre cases requires a vertical mast to balance the boat therefore side stays may (in this case - do) catch. On newer boats the mast is able to be raked further aft again due to centre case positioning (max aft) and will not catch..??

A couple of questions...
1. How much free rotation should a mast have... 180 degrees? I now have approximately 120 until the side stays grab where as before I changed the upper diamond attachment point I reckon I had maybe 60 degrees.
2. If I do rake the mast to clear the side stays how then do I balance the helm?
3. How do you guys insert a pic directly into the post like you have done..?? I can attach but have never worked out how to attach direct in a post.

I will chuck the mast up today in a raked position and see how it looks...

Cheers

Tim

See attached. This pic was taken today with the mast at the 4th hole down on the stay adjuster which calculated out to just over 4 degrees. I normally have it in the top hole which is no rake. As you can see the diamond wire still binds a little. There was actually very little difference between the non raked and 4 degree rake. You can imagine the trouble I had when the diamond wires were in the upper position as shown.